Conventionally known watchdog timers monitor the operation of a processor, such as a CPU, and reset the processor for example when the processor is in a runaway or frozen state. For example, JP H11-203173 A (PTL 1) discloses a watchdog timer circuit that causes a watchdog timer to operate only when the processor is in an operation mode (regular operation mode) and not during another standby mode (low current consumption operation mode).